Controllable coolant pump with an electro-hydraulic baffle plate adjustment

ABSTRACT

A controllable coolant pump of a cooling circuit for an internal combustion engine, having a pump housing, in which a pump shaft with associated impeller is rotatably arranged. The impeller conveys a coolant as a volume flow via an intake connection in a pressure or spiral channel of the coolant pump. The volume flow can be influenced by a baffle plate which encloses the outside of the impeller, the push rod of the baffle plate being guided in the pump shaft. In connection with an actuator the baffle plate can be continuously adjusted between two limit positions against the force of a spring. A control element, which has an electro-hydraulic action and which is integrated into the pump shaft, serves as an actuator, wherein the pressurized coolant in the coolant pump is provided as a hydraulic fluid.

The present invention relates to a controllable coolant pump of a cooling circuit of an internal combustion engine. A pump shaft, which includes an impeller and is preferably driven by a traction mechanism drive via an associated drive pulley, is rotatably supported in the pump housing of the coolant pump. The impeller conveys a coolant as a volume flow into a pressure or spiral channel of the coolant pump via an intake connection. The volume flow may be influenced by a baffle plate which surrounds the impeller on the outside and whose associated push rod is guided in the pump shaft. In connection with an actuator, the baffle plate may be continuously adjusted between two end positions against the force of a spring means.

BACKGROUND

For the purpose of cooling fluid-cooled, in particular water-cooled, internal combustion engines, a coolant or a cooling medium is pumped through cooling channels of the crankcase and the cylinder head of the internal combustion engine with the aid of a coolant pump in a closed circuit, and the heated cooling medium is subsequently recooled in an air-water heat exchanger. To support the circulation of the coolant, a coolant pump is used which is preferably driven directly by the internal combustion engine. Due to a direct coupling between the coolant pump and the crankshaft, a dependency of the pump rotational speed on the rotational speed of the internal combustion engine sets in. Consequently, the coolant circulates during a cold start of the internal combustion engine, thereby delaying a desired fast heating of the internal combustion engine. To optimize the operation of internal combustion engines, the fastest possible reaching of the operating temperature after the cold start is strived for. This makes it possible to reduce friction losses and fuel consumption and, at the same time, lower emission values. To achieve this effect, controllable coolant pumps are used whose delivered volume flow may be adapted to the cooling demand of the internal combustion engine. After a cold start, a zero delivery of the coolant pump is strived for, after which the volume flow destined for cooling the internal combustion engine increases continuously as a function of the temperature level which sets in. In a test series for optimizing the fuel consumption of internal combustion engines, it was possible to reduce fuel consumption by ≧3% by consequently implementing the aforementioned measures.

A controllable coolant pump for a cooling circuit of an internal combustion engine, which is driven by a traction mechanism drive, is known from DE 10 2008 046 424 A1. To influence the volume flow, the impeller is assigned an axially movable idler pulley, which is axially movable with the aid of a push rod placed within the hollow shaft of the impeller in connection with a final control element. The final control element includes an armature connected to the push rod, which is axially movable in a targeted manner via a proportional solenoid. The electrically actuatable final control element, or the actuator, is located on the front side upstream from the drive belt pulley of the coolant pump. DE 199 01 123 A1 describes another controlled coolant pump. To influence the volume flow, the impeller is assigned an outer, overlapping sliding element whose position may be changed by twisting a thread-like guide.

According to DE 10 2005 062 200 A1, the controlled coolant pump includes a shaft, which is supported and driven in the pump housing and has an associated impeller and a pneumatically or hydraulically adjustable valve slide, which variably covers an outflow area of the impeller. Multiple piston rods, which run in parallel to the pump shaft in the pump housing and are guided in annular grooves or bores and are sealed with the aid of rod seals in the pump housing, are situated on the valve slide, distributed over its circumference. The piston rods are operatively connected on the annular groove side to an annular piston which is inserted into a pressure chamber. The annual piston acted upon by pressure springs and the valve slider connected thereto are moved by applying pressure to the pressure chamber. A controllable coolant pump is known from DE 10 2005 004 315 A1, in which a volume flow is variable by a valve slide which surrounds the impeller and is movable on the pump shaft. The valve slide may be actuated with the aid of a solenoid armature which is acted upon by a solenoid coil and is movable on the pump shaft. The entire electrical adjusting device of the valve slide or the baffle plate, which surrounds the pump shaft, is situated within the pump housing between the impeller and a drive belt pulley of the coolant pump.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an installation space-optimized, robust device for a controllable coolant pump for adjusting the baffle plate to implement an effective control of the volume flow of the coolant pump.

The structure of the controllable coolant pump according to the present invention includes an electro-hydraulically operating final control element as an actuator, which is integrated into the pump shaft and with the aid of which a precise positioning of the baffle plate may be carried out to facilitate an active control of the volume flow or the coolant delivery quantity. The pressurized coolant of the coolant pump is provided as hydraulic fluid for the actuator. Integrating the actuator within the pump shaft reduces the required installation space for the coolant pump in both the radial and axial directions. Compared to previously known approaches, the present invention thus permits the implementation of a compact, installation space-optimized coolant pump. With the aid of the concept according to the present invention, it is possible, on the one hand, to ensure a gradual heating of the engine and, on the other hand, to influence the temperature of the internal combustion engine during continuous operation after the operating temperature has been reached. The friction losses and harmful emissions, and consequently the fuel consumption, may thus be significantly reduced within the entire operating range of the internal combustion engine.

The actuator may be advantageously pulsed in such a way that a rapid filling of a working chamber and/or pressure chamber with hydraulic fluid sets in for the purpose of quickly achieving a complete blocking of the volume flow to represent a zero delivery of the coolant pump after starting a cooled internal combustion engine. The volume flow which is triggered or influenced by the actuator for acting upon the pressure piston is greater than a hydraulic fluid leakage of the pressure chamber which sets in. The compact, simple and robust structure of the actuator according to the present invention may be advantageously manufactured and installed using a minimum amount of manufacturing and assembly work. Due to the protected installation location of the actuator integrated into the pump shaft, the operational reliability of the actuator, and consequently the reliability of the coolant pump, is improved. An advantageously high efficiency sets in with the aid of the compact actuator as well as a hydraulic system which uses the pressurized coolant of the coolant pump as hydraulic fluid. The approach according to the present invention is also designed in such a way that a coolant pump may be exchanged for coolant pumps presently being used, even in engines already manufactured today.

According to a preferred structural configuration of the present invention, the actuator includes a solenoid switch, which is positioned in a stationary manner and which acts directly upon a pump piston movable within the pump shaft. The solenoid switch of the actuator is preferably fastened in a stationary manner on the pump housing or a machine part assigned to the coolant pump, for example a crankcase of the internal combustion engine. In the installed position, the solenoid switch engages with clearance with an end-side receptacle of the pump shaft and is simultaneously supported on the pump piston via a centric switching axis. Together with the push rod or a pressure piston assigned to the push rod, the pump piston delimits the working chamber within the pump shaft, which is filled with hydraulic fluid and is designed as a cylinder. An axial movement triggered by the solenoid switch, a lift of the pump piston, is thus transmitted directly to the pressure piston, thereby triggering a synchronous adjustment of the baffle plate.

The structural configuration of the actuator hydraulics provides that the pressurized pressure medium flows, for example, out of the pressure or spiral channel of the coolant pump into the working chamber of the pump shaft via an inlet as a function of a position of the pump piston or as a function of pressure conditions which set it. A first variant according to the present invention provides that, in the de-energized state of the actuator, a pump piston position sets in which corresponds to an end position of the baffle plate in which a larger volume flow of the coolant pump sets in, which fills the working chamber via the inlet without hindrance. Upon actuation, i.e., energizing of the actuator, the inlet is closed by the lift of the pump piston associated therewith, which causes a pressure buildup in the working chamber to set in. An alternative configuration includes a one-way or check valve integrated into the inlet, which opens when a pressure difference or pressure gradient sets in. This state sets in upon a suction lift of the pump piston or if the solenoid switch of the actuator is de-energized, combined with a pressure gradient, which ensures a flow of pressure medium from the pressure or spiral channel into the working chamber of the pump shaft.

According to the concept according to the present invention, a one-way or check valve can be is-inserted into the end of the longitudinal bore hole forming the working chamber of the hydraulic system on the end facing away from the solenoid switch. The valve limits the pressure piston and the baffle plate connected thereto exclusively to a pressure medium flow, with the aid of which the baffle plate is adjusted in the direction of a closed impeller or a closed coolant pump. Ball valves are preferably suitable as one-way or check valves in the inlet and the working chamber of the coolant pump.

The structural configuration of the present invention furthermore may include includes a pressure piston having a cup-like design, which is connected to the baffle plate via the push rod and is guided in a centric stepped bore of the pump shaft. The push rod is axially movably guided in a receptacle or bore of a fixed-position guide bush of the pump shaft, a pressure spring being preferably inserted between the pressure piston and the guide bush as a spring means. To limit hydraulic fluid leaks, the pressure piston may be sealed against a stepped bore of the pump shaft.

Designing individual components of the actuator as a unit which may be preassembled suggests itself as a measure for simplifying assembly complexity. A cartridge or guide sleeve, which is designed to accommodate the pump piston, the one-way valve as well as a spring means inserted between the pump piston and the one-way valve and destined to act upon the pump piston in the direction of the solenoid switch, is advantageously suitable for this purpose. The preassembled structural unit may be subsequently inserted into the longitudinal bore of the pump shaft in a form-fitted and/or force-fitted manner.

According to the present invention, the switching or activation of the actuator may furthermore be combined with a control function for adjusting the baffle plate. Detecting at least one operating parameter of the internal combustion engine, in particular the coolant and/or lubricating oil temperature of the internal combustion engine, as a control variable and comparing it with a reference or guide temperature to purposefully carry out an adjustment of the baffle plate in the event of deviations, is preferably an option. A preferred control configuration includes a sensor system for detecting the temperature as well as a control unit which carries out the temperature compensation. In the event of a deviation, the solenoid switch of the actuator is activated by the control unit for the purpose of targeted adjustment of the baffle plate to influence the volume flow of the coolant pump and thus the operating temperature of the internal combustion engine.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features of the present invention are derived from the following description, in which two exemplary embodiments of the present invention are illustrated.

FIG. 1 shows a first exemplary embodiment of a coolant pump designed according to the present invention, having an actuator integrated into the pump shaft;

FIG. 2 shows a second exemplary embodiment of a coolant pump designed according to the present invention, having a baffle plate position in the de-energized state of the actuator;

FIG. 3 shows the coolant pump according to FIG. 2, having a baffle plate position that sets in when the actuator is in the de-energized state.

DETAILED DESCRIPTION

FIG. 1 shows a sectional view of a coolant pump 1, which may be preferably used for a coolant circuit of an internal combustion engine. A pump shaft 3, which is designed as a hollow shaft and is rotatably supported on two bearings 4, 5 designed, in particular, as roller bearings, is introduced into a pump housing 2 of coolant pump 1. First bearing 4 is inserted into a bore 6 of pump housing 2, and second bearing 5 is inserted between a shoulder of pump housing 2 and an axial receptacle of a belt pulley 7 rotatably fixed on pump shaft 3. Coolant pump 1 is driven by a traction mechanism drive 100 (shown schematically), a traction mechanism, a belt or a chain connecting drive pulley 7 to another drive pulley. An impeller 8, which is situated opposite drive pulley 7 on pump shaft 3, is assigned to an suction chamber 9, with the aid of which the coolant is radially conveyed as a volume flow into an annular or spiral chamber 102 (shown schematically) of pump housing 2 in the operating state of coolant pump 1. Suction chamber 9 is delimited by a cover disk 10, which simultaneously forms a transition to the spiral channel. To influence the volume flow of coolant pump 1, impeller 8 is assigned an axially movable baffle plate 11, which is supported directly on impeller 8 in a first end position, as shown in FIG. 1. A maximum volume flow of coolant pump 1 may be implemented in this baffle plate position, which corresponds to the largest opening. A zero delivery of coolant pump 1 sets in as soon as baffle plate 11 is supported on cover disk 10 in the second end position. Baffle plate 11 is rotatably rigidly connected to a push rod 12, which is linearly movable and positionable between the end positions or arbitrary intermediate positions, as illustrated by a double arrow. For this purpose, push rod 12 is guided in a bore 13 of a guide bush 14, which is pressed into a stepped bore 15 of pump shaft 3. Facing away from baffle plate 11, push rod 12 furthermore includes a pressure piston 16. An electro-hydraulically operating final control element, which is integrated into pump shaft 3, is used as actuator 17 to set or adjust baffle plate 11, the pressurized coolant of coolant pump 1 being provided as hydraulic fluid.

For this purpose, a solenoid switch 18 of actuator 17, which is fastened in a stationary manner to a machine part 20, for example the housing of the internal combustion engine, engages with clearance with an end-side receptacle 19 of pump shaft 3. A centric switching axis 21 of solenoid switch 18 is supported directly on a pump piston 22, which is movably guided in a cartridge 23, which is pressed into longitudinal bore 24 of pump shaft 3. Cartridge 23, which is designed as a cylindrical guide sleeve and extends over entire longitudinal bore 24, forms a working chamber 27 which is filled with hydraulic fluid and is axially delimited by pump piston 22 and a one-way valve 25, between which a spring means 26 applying an expanding force is inserted. In the baffle plate position illustrated in FIG. 1, a pressure level sets in in working chamber 27, which nearly corresponds to the pressure which sets in in the annular or spiral channel of pump housing 2 in the operating state. For this purpose, the hydraulic fluid may flow into the working chamber via an inlet 28 having an associated one-way valve 29. An actuation of solenoid switch 18 in the direction of the arrow causes a pressure rise in working chamber 27 as soon as one-way valve 29 is closed. At the same time, the hydraulic fluid flows through one-way valve 25 and acts upon a pressure chamber 31 which is axially delimited by pressure piston 16 and one-way valve 25, whereby push rod 12, which is connected to pressure piston 16, moves together with baffle plate 11 in the direction of cover disk 10. The actuating force of actuator 17 or solenoid switch 18 exceeds the spring force of spring means 26 acting directly upon pump piston 22 as well as the spring force of a second spring means 30 inserted between pressure piston 16 and guide bush 14. In the de-energized state of solenoid switch 18, spring means 26 causes pump piston 22 to automatically return to the position corresponding to FIG. 1. Baffle plate 11 initially remains in the set position, since one-way valve 25 prevents the hydraulic fluid from flowing back from pressure chamber 31.

Due to a hydraulic fluid leak, which sets in, in particular between pressure piston 16 and stepped bore 15 of pump shaft 3, supported by a spring force of spring means 30, baffle plate 11 is pushed more slowly in the direction of pump housing 2 via pressure piston 16 in the de-energized state of solenoid switch 18. Another pump cycle begins as soon as solenoid switch 18 is energized again. If solenoid switch 18 is energized in a pulsed manner, working chamber 27 is pumped up continuously. Solenoid switch 18 of actuator 17 and its pulsing are designed in such a way that a fast filling of working chamber 27 and consequently of pressure chamber 31 with hydraulic fluid is ensured. When starting a cooled internal combustion engine, an active contact of baffle plate 11 on cover disk 10 may be ensured to achieve a complete blocking of the volume flow, i.e., a zero delivery of coolant pump 1. The volume flow triggered by solenoid switch 18 of actuator 17 for acting upon pressure piston 16 is designed to be greater than a hydraulic fluid leakage of pressure chamber 31 which sets in.

FIGS. 2 and 3 show a cutout of coolant pump 1 having an alternatively designed, electro-hydraulically operating actuator 37. The following description relates to the distinguishing features between the first variant according to FIG. 1 and the second variant illustrated in FIGS. 2 and 3, the components or areas corresponding to FIG. 1 being provided with the same reference numerals.

According to FIGS. 2 and 3, inlet 38 does not include a one-way valve in working chamber 47, so that hydraulic fluid is able to flow directly into working chamber 47 via inlet 38, depending on the position of pump piston 32. FIG. 2 shows pump piston 32 in a position which blocks inlet 38, this position being taken in the de-energized state of solenoid switch 18 of actuator 37. Deviating from FIG. 1, pump piston 32, spring means 26 and one-way valve 45 are guided directly in longitudinal bore 34 of pump shaft 33. As soon as inlet 38 is closed, at least a partial quantity of the hydraulic fluid is displaced out of working chamber 47 and into pressure chamber 48 through opened one-way valve 45, due to the actuation of pump piston 32, and pressure piston 36, including push rod 42 and baffle plate 41, is consequently displaced. To reduce leaks, pressure piston 36 is inserted into stepped bore 35, forming a seal and, for this purpose, forms a circumferential annular groove 39, into which a sealing ring 44 is inserted. Opposite pressure chamber 51 a spring means 40 is inserted within stepped bore 35 of pump shaft 33 between guide bush 46, which is positioned in a stationary manner and connected to a carrier element 43, push rod 42 and pressure piston 36. A bore 50, which is radially offset with respect to guide 49 for push rod 41, is introduced into guide bush 46, via which a pressure compensation takes place during the actuations of pressure piston 36. FIG. 3 shows the position of pump piston 32 as well as baffle plate 41 in the de-energized state of solenoid switch 18 of actuator 37. Pump piston 32 is in an end position which facilitates a flowing of hydraulic fluid into working chamber 47 via inlet 38. At the same time, baffle plate 41 is in a position whereby a maximum volume flow of coolant pump 1 sets in.

LIST OF REFERENCE NUMERALS

-   1 coolant pump -   2 Pump housing -   3 Pump shaft -   4 Bearing -   5 Bearing -   6 Bore -   7 Drive pulley -   8 Impeller -   9 Suction chamber -   10 Cover disk -   11 Baffle plate -   12 Push rod -   13 Bore -   14 guide bush -   15 Stepped bore -   16 Pressure piston -   17 Actuator -   18 Solenoid switch -   19 Receptacle -   20 Machine part -   21 Switching axis -   22 Pump piston -   23 Cartridge -   24 Longitudinal bore -   25 One-way valve -   26 Spring means -   27 Working chamber -   28 Inlet -   29 One-way valve -   30 Spring means -   31 Pressure chamber -   32 Pump piston -   33 Pump shaft -   34 Longitudinal bore -   35 Stepped bore -   36 Pressure piston -   37 Actuator -   38 Inlet -   39 Annular groove -   40 Spring means -   41 Baffle plate -   42 Push rod -   43 Carrier element -   44 Sealing ring -   45 One-way valve -   46 Guide bush -   47 Working chamber -   48 Pressure chamber -   49 Guide -   50 Bore -   100 Traction mechanism drive -   102 Pressure channel 

1-9. (canceled)
 10. A controllable cooling pump of a cooling circuit of an internal combustion engine, comprising: a pump housing; a rotatably supported pump shaft connected to an impeller driven by a traction mechanism drive via an associated drive pulley, the impeller conveying a coolant as a volume flow into a pressure or spiral channel of the coolant pump via an intake connection; a baffle plate capable of influencing the volume flow, the baffle plate encompassing the impeller on the outside and a push rod associated with the baffle plate being guided in the pump shaft, and the baffle plate being continuously adjustable between two end positions against the force of a spring in connection with an actuator; the actuator being an electro-hydraulically operating final control element integrated into the pump shaft and provided for positioning the baffle plate, with the aid of which a working chamber or a pressure chamber is filled with pressurized coolant of the coolant pump as hydraulic fluid.
 11. The coolant pump as recited in claim 10 wherein the actuator has a solenoid switch, the actuator positioned in a stationary manner, the solenoid switch acting upon a pump piston guided directly or indirectly in a longitudinal bore of the pump shaft designed as a hollow shaft, the pump piston together with the push rod or a pressure piston assigned to the push rod delimiting the working chamber of the pump shaft, which is filled with hydraulic fluid.
 12. The coolant pump as recited in claim 11 wherein the solenoid switch engages with an end-side receptacle of the pump shaft, and its centric switching axis interacts with the pump piston.
 13. The coolant pump as recited in claim 10 wherein the hydraulic fluid flows into the working chamber of the pump shaft via an inlet as a function of a position of a pump piston.
 14. The coolant pump as recited in claim 10 wherein the hydraulic fluid flows into the working chamber of the pump shaft via a one-way valve integrated into the inlet in the event of a pressure difference or a pressure gradient.
 15. The coolant pump as recited in claim 11 further comprising a one-way valve allowing a pressure medium to flow in the direction of the pressure piston inserted into the end of the longitudinal bore of the pump shaft on the end facing away from the solenoid switch.
 16. The coolant pump as recited in claim 10 wherein a pressure piston connected to the baffle plate via a push rod is guided in a stepped bore of the pump shaft, the push rod being movable in a positionally fixed guide bush of the pump shaft, a spring being inserted between the pressure piston and the guide bush.
 17. The coolant pump as recited in claim 10 further comprising a cartridge or guide sleeve pressed into the longitudinal bore of the pump shaft, which is designed to accommodate a pump piston, a one-way valve as well as a spring inserted between the pump piston and the one-way valve.
 18. The coolant pump as recited in claim 10 wherein an actuation of the actuator is controlled as a function of at least one operating parameter of an internal combustion engine. 